After careful consideration of all the evidence I believe the titles mean all of these.
Red and Blue color scheme- Genetics and 3D The double helix-Genetics and the 3D shape on a plane that is point X, Y, and Z. Bird Pokemon Y-Sky Y chromosome and Point Y Deer Pokemon X-Land X chromosome and Point X
With this in mind the third should be a sea based with a Z shape, a serpent/dragon could easily fit this motif. In addition to keep with the genetics we have XX and XY chromosome pairs.
Ultimately what I'm going to bank on right now is pokemon ZXX and pokemon ZXY.
I've got a quote that embodies you perfectly, but it's seventy-three posts long, has a few massive flowcharts, and lots of Xion-KMA to Me